|
|
Bulava, J., Della Morte, M., Heitger, J., & Wittemeier, C. (2016). Nonperturbative renormalization of the axial current in N-f=3 lattice QCD with Wilson fermions and a tree-level improved gauge action. Phys. Rev. D, 93(11), 114513–7pp.
Abstract: We nonperturbatively determine the renormalization factor of the axial vector current in lattice QCD with N-f = 3 flavors of Wilson-clover fermions and the tree-level Symanzik-improved gauge action. The (by now standard) renormalization condition is derived from the massive axial Ward identity, and it is imposed among Schrodinger functional states with large overlap on the lowest lying hadronic state in the pseudoscalar channel, in order to reduce kinematically enhanced cutoff effects. We explore a range of couplings relevant for simulations at lattice spacings of approximate to 0.09 fm and below. An interpolation formula for Z(A)(g(0)(2)) , smoothly connecting the nonperturbative values to the 1-loop expression, is provided together with our final results.
|
|
|
|
Donini, A., Hernandez, P., Pena, C., & Romero-Lopez, F. (2016). Nonleptonic kaon decays at large N-c. Phys. Rev. D, 94(11), 114511–6pp.
Abstract: We study the scaling with the number of colors, N-c, of the weak amplitudes mediating kaon mixing and decay. We evaluate the amplitudes of the two relevant current-current operators on the lattice for N-c = 3-7. We conclude that the subleading 1/N-c corrections in B-k, are small, but those in the K -> pi pi amplitudes are large and fully anticoirelated in the I = 0, 2 isospin channels. We briefly comment on the implications for the Delta I = 1/2 rule.
|
|
|
|
Lu, J. X., Chen, H. X., Guo, Z. H., Nieves, J., Xie, J. J., & Geng, L. S. (2016). Lambda(c)(2595) resonance as a dynamically generated state: The compositeness condition and the large N-c evolution. Phys. Rev. D, 93(11), 114028–16pp.
Abstract: Recent studies have shown that the well-established Lambda(c) (2595) resonance contains a large meson-baryon component, which can vary depending on the specific formalism. In this work, we examine such a picture by utilizing the compositeness condition and the large number of colors (N-c) expansion. We examine three different models fulfilling two body unitarily in coupled-channels, and adopting renormalization schemes where the mass of the Lambda(c)(2595) resonance is well described, but not necessarily its width, since we do not consider three body channels and work at the isospin symmetric limit. Both approximations might have an effect larger on the width than on the mass. In this context, our studies show that the compositeness of the Lambda(c)(2595) depends on the number of considered coupled channels, and on the particular regularization scheme adopted in the unitary approaches and, therefore, is model dependent. In addition, we perform an exploratory study of the Lambda(c)(2595) in the large N-c expansion, within a scheme involving only the pi Sigma(c) and K Xi(c)', channels, whose dynamics is mostly fixed by chiral symmetry. In this context and formulating the leading-order interaction as a function of N-c, we show that for moderate N-c > 3 values, the mass and width of the Lambda(c)(2595) deviate from those of a genuine qqq baryon, implying the relevance of meson-baryon components in its wave function. Furthermore, we study the properties of the Lambda(c)(2595), in the strict N-c -> infinity limit, using an extension of the chiral Weinberg-Tomozawa interaction to an arbitrary number of flavors and colors. This latter study hints at the possible existence of a (perhaps) subdominant qqq component in the Lambda(c)(2595) resonance wave function, which would become dominant when the number of colors gets sufficiently large.
|
|
|
|
Ortega, P. G., Segovia, J., Entem, D. R., & Fernandez, F. (2016). Canonical description of the new LHCb resonances. Phys. Rev. D, 94(11), 114018–7pp.
Abstract: The LHCb Collaboration has recently observed four J/psi phi structures called X(4140), X(4274), X(4500), and X(4700) in the B+ -> J/psi phi K+ decays. We study them herein using a nonrelativistic constituent quark model in which the degrees of freedom are quark-antiquark and meson-meson components. The X(4140) resonance appears as a cusp in the J/psi phi channel due to the near coincidence of the D-s(+/-) D-s(*+/-) and J/psi phi mass thresholds. The remaining three [X(4274), X(4500), and X(4700)] appear as conventional charmonium states with quantum numbers 3(3)P(1), 4(3)P(0), and 5(3)P(0), respectively, and their masses and widths are slightly modified due to their coupling with the corresponding closest meson-meson thresholds. A particular feature of our quark model is a lattice-based screened linear confining interaction that has been constrained in the light-quark sector and usually produces higher excited heavy-quark states with lower masses than standard quark model predictions.
|
|
|
|
Molina, R., Doring, M., & Oset, E. (2016). Determination of the compositeness of resonances from decays: The case of the B-s(0) -> J/Psi f(1)(1285). Phys. Rev. D, 93(11), 114004–10pp.
Abstract: We develop a method to measure the amount of compositeness of a resonance, mostly made as a bound state of two hadrons, by simultaneously measuring the rate of production of the resonance and the mass distribution of the two hadrons close to threshold. By using different methods of analysis we conclude that the method allows one to extract the value of 1-Z with about 0.1 of uncertainty. The method is applied to the case of the (B) over bar (0)(s) -> J/Psi f(1)(1285) decay, by looking at the resonance production and the mass distribution of K (K) over bar*.
|
|
